Process for oil distillation



July 8, 1930. c. F. TEARS PROCESS FOR OIL DISTILLATION Filed April 23, 1923 2 Sheets-Sheet 1 mx k bau kvsw gnvento'c f. rm

July 8, 1930. c. F. TEARS PROCESS FOR OIL DISTI LLATION Filed April 23, 1923 2 Shaotu-Shqet 2 Patented July 8, 1930 UNITED STATES Parser oF Ic CLAUDE IF; TEARS, OF WEST NEW BRIGHTON, NEW YORK, ASSIGNOB, BY MESNE ASSIGNMENTS, TO THE TEXAS COMPANY, OF NEW YORK, N. Y., A. CORPORATION OF DELAWARE PROCESS FOR OIL DISTILLATION Application filed April 23,

This invention relates to processes for the distillation of oils, and it has special reference to the continuous distillation of crude oil and the separation thereof into predetermined fractions or cuts by passing the evolved vapors successively through aseries of insulated fractionating towers or columns that are preferably disposed the one above the other and so arranged that certain portions of the liquid condensed therein are delivered into the towers immediately below for further distillation or treatment.

One of the objects of the invention is to improve and simplify the construction and operation of systems of this general character and to provide a process and apparatus that is especially adapted for continuous and efficient operation and for the selective separation of the desired fractions or condensates through extremely close and accurate fractionation by means of 'fractionating bubble or boiling cap towers to produce fractions closely conforming to the desired .boiling point ranges.

These and other objects and features of the invention will be more readily understood from the following description of an illustrative embodiment thereof shown in the accompanying drawings of which:

Fig. 1 and FigNP, taken together, diagrammatically constitute a view in side elevation, with certainportions broken away,

of an apparatus constructed in accordance with the invention and particularly adapted for practicing the process involved, and

Fig. 2 is an enlar ed sectionalelevation of a portion of one o the combined heat exchangers and bubble tower units utilized in the system and process.

Referring to the drawings, the apparatus shown comprises, in general, a furnace 10 in which is mounted a still 12 containing a body of 'oil to be distilled; a plurality of insulated fractionating towers in the form of bubble towers 14, 16, 18 and 20 connected in series relation to the still and through which the evolved vapors are'passed and fractionally separated; a plurality of heat exchangers 22, 24 and 26 that are associated and combined with the bubble towers 16, 18 and 20, respec- 1923. Serial No. 633,820.

oil into the system; a heat exchanger 36 associated with thecharginline and the residual oil draw-oft line or effecting a heat exchange between the residual oil and the charging stock; a cooling device 38 for reducing the temperature of the residual oil emerging from the heat exchanger 36, and

a plurality of cooling devices-40, 42 and 44 Y for reducing the temperature of the eflluents or condensates removed from the lower ends of the respective bubble towers 16, 18 and 20.

The furnace 10 and the still 12 may be of any suitable and well known construction for effecting the distillation of a body of oil. The stillis provided near its bottom with a pipe 46b means of which steam may be in troduced Into the oil in accordance with usual practice.

As the distillation of the oil continues, it is desirable to draw off the heavy residual oil from the bottom of the still through the draw-ofi' line 32 and inasmuch as fresh charging stock is preferably .continuously admitted into the still, as will be hereinafter more fully described, the liquid level of the oil therein is maintained substantially constant by automatically withdrawing the residual oil from the bottom through the agency of an automatic float controlled valve 47 that is disposed in the draw-off line 32. The operation of this valve is effected and controlled by means of a suitable float 48 within the still, the movements of which are transmitted thereto through suitable mechanism 49. The automatic valve 4:? is by-passed by a valve 47.

The draw-off line 32 delivers the heated residual oil into one end of the heat exchanger 36, comprising a casing 50 and a plurality of tubes 51 disposed therein. The heated oil traverses the tubes 51 and is discharged from the other end, of the exchanger through a pipe 52 into the cooler 38 by means through which the oil may be delivered,

of which the temperature'of the residual oil is reduced before it is delivered throu h a pipe 53 to storage. The casing 50 of the heat exchanger 36 forms around the tubes 51 a jacket into which fresh charging oil is introduced through the charging line 34. During the traverse of the charging stock throu h the jacket of the heat exchanger, a trans er of heat is effected from the residual oil to the charging stock whereby said charging stock is reheated. This preheated charging stoc emerges from 1 the heat exchanger through the pipe 54, containing a valve 1 desired, directly to the-still 12, although it is preferred to close the valve? 55-and introduce the preheated charging oil through branch line 56 and valve 57. into the first bubble -conducted through tower 14. As the distillation of the oil in the still 12 proceeds, the evolved vapors are with= drawnthrougha vapor line and delivered into the bottom of the first bubble tower 14, through which the vapors traverse in countercurrent relation to the flow of the condensate accumulating within the tower and progressively gravitating towards its bottom. Such of the vapors as are not condensed in the bubble tower 14 pass on and are successively the remaining bubble towers 16. 18 and 20 and their associated heat exchangers 22, 24 and 26, while the lightest constituents, uncondensed in the towers, are carried through the condensers 28 and 30 and are finally collected.

The bubble tower 14 may be of any conventional construction, such as are common in the art. In fact, any form of fractionating towers may be used, although bubble towers are preferred. The bubble tower 14 as shown embodies a construction similar to that shown inthe upper portion of Fi 2, which illustrates oneof the combined heat exchanger and bubble tower units employed in the system. The preferred construction of the bubble tower 14 will be understood from the following descri tion of one of the combined exchanger and ubble tower units. These units are of like construction and a. description of the first unit, combining the butlgible tower 16 and heat exchanger 22, will su ce.

With particular reference to Fig. 2, the,

unit therein illustrated, comprises the bubble tower 16 whichis disposed above and asso' ciated with the heat exchanger 22. The hubble tower embodies a plurality of sections or plates 64 that are disposed the one above the other and which communicate with one another by means of a series of upstanding vapor pipes 66, that are provided with caps 67 over their upper ends for the purpose of deflecting the vapors arising therethrough and directing them downwardly beneath pools of liquid oil 68 maintained therein.

gents contained The bottom edges: of the caps 67 are preferably serrated to assist in effecting a uniform distribution of the vapors. In order to maintain a predetermined level of the pool 68 of liquid oil in each of the sections of the bubble tower,

delivering excess oil into the pools of oil in the sections below. From this construction, it will be understood that the vapors that are delivered to the bubble tower, or which are distilled from the portions of oil disposed therein, are caused to successively pass upwardly through thence are directed downwardly by the Caps 67, whence they emerge through the serrated edges thereof and bubble up through the pools of oil in the several sec-' tions. The heavier constituents of the vapors are condensed during this process, while the heat of the vapors assists in vapor-' izing or distilling off any lighter constituin the pools of liquid. ,Any number of bubble tower sections may be employed, depending upon the character of the oil under treatment, the operating conditions, and the distillation range of the particular fraction or cut that it is desired to separate and collect as a condensate or efliuent. It will be understood that the vapors tend to pass upwardly through the several pools of oil in the sections, and such of the vapors as are not condensed during this operatlon, accumulate at the upper end of the tower and are passed on for subsequent treatment in the next succeeding tower. On the other hand,

overflow pipes 69 are provided for the vapor pipes 66 and I the condensate that gradually accumulates in the several pools in the respective bubble vv tower sections progressively overflows and passes downwardly through the preceding lower sections.

. The heat exchanger 22 is disposed directly beneath the lower section 64* and comprises nicate with a section 74 disposed beneath the heat exchanger 22. The liquid oil which is delivered by overflow pipe 69 into the lower section 64 of the bubble tower, is then permitted to'fiow downwardly through the various tubes 71 and into the lower collecting "section 74, which is provided with a draw off line 75 for the purpose of removing the "condensate or effluent therefrom.- to insure that the tubes 71 of the heat exchanger are filled with oil, the oil level is automatically maintained in the lower section 64 above the upper ends of the tubes by means of float controlled valve 76 disposed in the draw-off line 7 5 and operated in accordance with the movements of a float 77 in any suitable manner.

In order The casing 70, enveloping the tubes 71 of the heat exchanger, forms a jacket into which vapors are introduced through a vapor line 78, the vapors passing around and in contact with the several pipes, beingdirected in their flow by a plurality of baflies 79 disposed within the casing. The vapors are conducted away from the heat exchanger casing by means of an outlet vapor line 80. During the traverse of the vapors through the heat'exchanger in contact with the tubes 71, some of the heat thereof is given up and absorbed by the liquid condensate contained in the tubes, While the temperature of the vapors is correspondingly reduced. The heat thus absorbed by the condensate serves to vaporize certain of the lighter constituents thereof, which pass upwardly through the tower, depending, of course, upon their volatility. During this process, the

vapors within the casing lose'some of theirheat and certain constituents thereof are condelivered thereto and pass upwardly there-- through in counter-current relation to the downwardly flowing liquid oil and condensate. As already stated, it is preferred to introduce the preheated charging oil through,

the line 56 into the bubble tower 14:, and connections to the bubble tower may be effected through either of the valved branch lines 83 or 84, depending upon which of thesections is to be utilized. Of course, certain of the lighter constituents of the charging oil will be vaporized in the residual oil heat exchanger 36 and such portions, upon entrance into the bubble tower rise through such of the remaining sections as their volatility will per- .mit. The portions of the charging oil of lower volatility on the other hand, pass downwardly through the overflow pipes of the various sections, being in part va prized and in part raised to progressively igh'er temperatures as it gravitates to the lower end thereof, Such portions of the charging oil,-

together with such condensate as may reach the lower end of the tower, is backtrapped to the still through the line 85.

The vapors that emerge from the top of the bubble tower 14 are carried throughthe vapor line 78 leading to the heat exchanger 22 that is combined with the bubble tower 16 of the next succeeding unit. These vapors pass-through the heat exchanger 22 in the manner already described and are thence de livered by the vapor line 80 to an intermediate enlarged section 64" of the bubble tower 16. Such liquid oil as accumulates within the heat exchanger casing is run back through pipe 82 to the upper end of the preceding bubble tower 14 where it serves as a reflux medium and mingles with the pool of oil in the upper section and, is subjected to further treatment.

either proceed in. the manner already de- The vapors entering the inter .mediate section 64* of the bubble tower 16 scribed through the upper section thereof or are condensed and gravitate downwardly through the lower sections and finally pass throu h the exchanger pipes 71 to be ultimate- 1y wit drawn through the pipe 75 containing the automatic float operated valve 7 6, as one of the desired fractions, for instance,gas oil. This condensate fraction is reduced in temperature by passing it through the cooler 40 and is thereafter collected or run tottorage.

In a similar manner such vaporsas emerge from the top ofthe bubble tower-'16 are con-.

ducted bywapor line 88 to and through the heat exchanger 24 and bubble tower 18 of the next succeeding unit, which functions in a like manner and produces a condensate fraction of the desired volatility, such as kerosene, which is drawn oil and passed through the cooler 42 to storage. Such of the vapors'as condense in the heat exchanger 24 are conducted through pipe 89 to the upper-section of the preceding bubble tower 16.

In an analogous manner the o eration continues, and the vapors are passe through the succeeding unit which separates out the next lighter fractional condensate or efli-uent, such as naphtha, which is drawn off and passed through the cooler 44 to storage.

Such of the oil vapors, as for instance gasoline, that emerge from the top of the last bubble tower 20 of the series, are conducted through vapor line 90 into the upper end of the water-cooled condenser 28 throu h which they pass around the cooling pipes 9 and are thence conducted by vapor line 92 to the upper end of the water-cooled condenser 30.

Certain of the higher boilingconstituents of'these vapors will condensein condenser 28 and are reintroduced into the top of the bubble tower 20 by means of pipe 93 for further treatment. The remaining vapors delivered to the condenser 30 are condensed therein and are withdrawn through the pipe 94 to storage as the final condensate or fraction, such as gasoline. The extremely light orwild gases and vapors that are non-condensable in the condenser 30 may be taken off through pipe 95 and, if desired, passed through suit able scrubbers.

From the foregoing description, it'will be understood that a continuous process'of distillation and fractional condensationis carried out in an extremely eflicient manner to produce a plurality of cuts or fractions in the form of condensates or distillates that-a are fractionated with extreme closeness and selectivity whereby the boiling point ranges of the various fractions closely conform to the desired and predetermined ranges.

While, for convenience, the invention has been described in connection with the distillation of crude oil and the selective separation of lubricating oil, gas oil, kerosene, naphtha and gasoline fractions, it will be'understood that these terms are merely used in an exemplary manner and should not be literally construed as restricting the scope of the invention. Moreover, the details of construction, the arrangement and location of parts and the mode of operation may be varied considerably within the spirit and scope of the invention and, therefore, only such limitations should be imposed asare indicated in the appended claims. 20 .What I claim is:

. a 1. -A rocess of oil distillation that comprises distillin a body of oil in a still, passing the evolved vapors successively through a series of bubble towers for close fractionation and separation of predetermined condensates, continuously delivering fresh charging oil into the first bubble tower of the vseries, backtrapping into the still such of the chargingoil and condensate as accumulates .at the bottom of the first bubble tower, eflecting a heat exchange between the rising vapors and the gravitatin' condensate in .transit between the other bub le towers to produce a reflux medium, removing said redetermined condensates from all but the rst bubble tower of the series, and back-trapping to the preceding bubble tower to serve as' a which predetermined fractions are separated, wit drawing hot residual oil from the still to maintan a substantially constant liquid level therein, passing the hot residual oil drawn from the still in heat exchange relation with the charging oil to. preheat said charging oil, charging said preheated oil into the first bubble tower of the series, back-trapmediate point in-the next succeeding bubble tower, and back-'trappin only the condensed vapors liquefied by said. eat exchange to the preceding bubble tower of the series to serve as a reflux medium therefor.

In witness whereof I have hereunto set my hand this 14th day of April, 1923.

CLAUDE F. TEARS.

reflux medium therefor only the condensed I vapors liquefied by said heat exchange.

2. A rocess of oildistillation that comprises distilling a body of oil in a still, continuously deliver ng oil to the still to maintain a constant liquid level therein, successively 4 passing theevolved vapors throu h'a. lurality of bubble towers to effect a c ose ractionation thereof, back-trapping the condensate from the first bubble tower of the series to the still, passing the vapors emerging from each bubble tower of the'series in heat exchange relation with the gravitating condensate from the next succeeding bubble tower of the series to produce a reflux me.-

dium, drawing off the respective condensates 7 from the several bubble towers except the first, passing the vapors uncondensed-by'the heat exchange into an intermediate point in the next succeeding bubble tower, and backtrappin only the condensed vapors liquefied by said eat exchange to the preceding hub- 60 ble tower of the series to serve as a reflux medium therefor. p

3. A process of oil distillation that comprises distillin a body of oil in a still, passing the evolved vapors successively through a series of fractionating bubble towers in ping into the still such of the charging oil and 

